Laura K. Povlich

Recent advances in fluorescent and colorimetric conjugated polymer-based biosensors

Conjugated polymers recently have drawn much attention as an emerging sensory material due to their meritorious signal amplification, convenient optical detection, readily tunable properties, and easy fabrication. We review the molecular design principles of sensory conjugated polymer recognition events, which can trigger conformational change of the conjugated polymer, induce intermolecular aggregation, or change the distance between the conjugated polymer as an energy donor and the reporter dye molecule as an energy acceptor. These recognition/detection mechanisms result in mainly three types of measurable signal generation: turn on or turn off fluorescence, or change in either visible color or fluorescence emission color of the conjugated polymer. In this article, we highlight recent advances in fluorescent and colorimetric conjugated polymer-based biosensors.

In situ polymerization of a conductive polymer in acellular muscle tissue constructs

We present a method to chemically deposit a conductive polymer, poly(3,4-ethylenedioxythiophene) (PEDOT), on acellularized muscle tissue constructs. Morphology and structure of the deposition was characterized using optical and scanning electron microscopies (SEM). The micrographs showed elongated, smooth, tubular PEDOT structures completely penetrating and surrounding the tissue fibers. The chemical polymerization was performed using iron chloride, a mild oxidizer. Remaining iron and chlorine in the tissue constructs were reduced to acceptable metabolic levels, while preserving the structural integrity of the tissue. We expect that these acellular, polymerized tissue implants will remain essentially unmodified in cellular environments in vitro and in vivo because of the chemical and thermal stability of the PEDOT polymer depositions. Our results indicate that in situ polymerization occurs throughout the tissue, converting it into an extensive acellular, non-antigenic substrate of interest for in vivo experiments related to nerve repair and bioartificial prosthesis. We expect these conducting polymer scaffolds to be useful for direct integration with electronically and ionically active tissues.

Synthesis, copolymerization and peptide-modification of carboxylic acid-functionalized 3,4-ethylenedioxythiophene (EDOTacid) for neural electrode interfaces☆

BACKGROUND Conjugated polymers have been developed as effective materials for interfacing prosthetic device electrodes with neural tissue. Recent focus has been on the development of conjugated polymers that contain biological components in order to improve the tissue response upon implantation of these electrodes. METHODS Carboxylic acid-functionalized 3,4-ethylenedioxythiophene (EDOTacid) monomer was synthesized in order to covalently bind peptides to the surface of conjugated polymer films. EDOTacid was copolymerized with EDOT monomer to form stable, electrically conductive copolymer films referred to as PEDOT-PEDOTacid. The peptide GGGGRGDS was bound to PEDOT-PEDOTacid to create peptide functionalized PEDOT films. RESULTS The PEDOT-PEDOTacid-peptide films increased the adhesion of primary rat motor neurons between 3 and 9 times higher than controls, thus demonstrating that the peptide maintained its biological activity. CONCLUSIONS The EDOT-acid monomer can be used to create functionalized PEDOT-PEDOTacid copolymer films that can have controlled bioactivity. GENERAL SIGNIFICANCE PEDOT-PEDOTacid-peptide films have the potential to control the behavior of neurons and vastly improve the performance of implanted electrodes. This article is part of a Special Issue entitled Organic Bioelectronics-Novel Applications in Biomedicine.

Electroactive Polymeric Biomaterials

Conjugated polymers are attractive materials for interfacing electrically conducting devices with biological tissue. These polymers, which can be electrochemically polymerized on metal electrodes, are electrically and ionically conductive, mechanically softer than metals, and have low cytotoxicity. The surface area of conjugated polymers can be tailored to create films with low electrical impedance. In addition, through synthetic chemistry or electrochemical doping, biological molecules can be incorporated into conjugated polymer films. These properties enable conjugated polymers to effectively interface with ionically active tissues, most often nervous tissue. This chapter will focus on the conjugated polymers that have received the most attention for interfacing with tissue, polypyrrole (PPy) and poly(3,4-ethylenedioxythiophene) (PEDOT). Derivatives of these polymers that can covalently bind to biological molecules, such as peptides, have been developed, along with composites of the polymers with hydrogels, which have greater tissue-like properties. Coatings of PPy and PEDOT have been put on devices, including neural probes, and made into fibers for neural regeneration. Many current research projects focus on addressing biological reactions that occur upon implantation of devices, such as inflammation and gliosis. Potential solutions to these problems include electrical actuation of conjugated polymers for drug delivery and in vivo electrochemical polymerization.